<!DOCTYPE html>
<html lang="zh-cn">
<head>
    <meta charset="UTF-8">
    <meta name="keywords" content="生鲜, 电商, 水果, 蔬菜, 肉类, 海鲜">
    <meta name="description" content="这是一个生鲜电商平台示例页面">
    <meta name="author" content="作者名">
    <title>生鲜电商平台</title>
    <style>
        body {
            font-family: "楷体", "KaiTi";
            margin: 0;
            padding: 0;
        }
        .clear {
            clear: both;
        }
        .circle-box {
            width: 100px;
            height: 100px;
            background-color: lightblue;
            border: 5px solid blue;
            border-radius: 50%;
            padding: 20px;
            margin: 20px;
            box-shadow: 0 4px 8px rgba(0, 0, 0, 0.2);
        }
        .form-container {
            margin: 20px;
            padding: 20px;
            border: 1px solid #ccc;
            box-shadow: 0 4px 8px rgba(0, 0, 0, 0.2);
        }
        .form-container input {
            display: block;
            margin-bottom: 10px;
            padding: 10px;
            width: 100%;
            box-sizing: border-box;
        }
        .back-to-top {
            position: fixed;
            bottom: 10px;
            right: 10px;
            width: 50px;
            height: 50px;
            background-color: #333;
            color: white;
            text-align: center;
            line-height: 50px;
            border-radius: 50%;
            cursor: pointer;
        }
        .relative-box {
            position: relative;
            width: 200px;
            height: 200px;
            background-color: lightgreen;
            margin: 20px;
        }
        .absolute-box {
            position: absolute;
            top: 50px;
            left: 50px;
            width: 100px;
            height: 100px;
            background-color: lightcoral;
        }
        .container {
            width: 100%;
            padding: 20px;
            box-sizing: border-box;
        }
        .box {
            width: 100px;
            height: 100px;
            background-color: lightblue;
            text-align: center;
            line-height: 100px;
            float: left;
            box-sizing: border-box;
        }
        .box-margin {
            margin-left: 10px;
            margin-right: 10px;
            background-color: lightcoral;
        }
        .box-position {
            position: relative;
            left: 10px;
            background-color: lightgreen;
        }
        .box-float {
            float: right;
            background-color: lightyellow;
        }
    </style>
</head>
<body>
    <div class="clear"></div>

    <!-- 圆形盒子 -->
    <div class="circle-box"></div>

    <!-- 表单 -->
    <div class="form-container">
        <form>
            <input type="text" placeholder="姓名">
            <input type="email" placeholder="邮箱">
            <input type="password" placeholder="密码">
            <input type="submit" value="提交">
        </form>
    </div>

    <!-- 绝对定位和相对定位 -->
    <div class="relative-box">
        <div class="absolute-box"></div>
    </div>

    <!-- 使用 margin、position、float 对齐的盒子 -->
    <div class="container">
        <div class="box">Box 1</div>
        <div class="box box-margin">Box 2 (Margin)</div>
        <div class="box box-position">Box 3 (Position)</div>
        <div class="box box-float">Box 4 (Float)</div>
        <div class="clear"></div>
    </div>

    <!-- 固定定位的返回顶部按钮 -->
    <div class="back-to-top">↑</div>

</body>
</html>
